Table 1.

Summary of Studies Evaluating Intermediate Variables in the Association Between Black/White Race and Occurrence of Very Preterm Birth or Very Low Birth Weight

Author, Year, (Reference No.)	Outcome	Pathwaya	Results
Simhan, 2003 (156)	VPT birthb	Genotype/epigenetics	The interleukin-6 polymorphism was protective against VPT birth in white women, but single-nucleotide polymorphism was not present in black women cases or controls in the study.
Catov, 2007 (138)	VPT birthb	Preconceptional health	Periconceptional multivitamin use was protective against VPT birth and was less prevalent among black women than white women.
Ehrenthal, 2007 (102)	VPT birthc VLBWd	Preconceptional health	Although black women had a higher prevalence of preconceptional hypertension and diabetes than white women did, control for preconceptional health status did not appreciably reduce the racial disparity.
Khoshnood, 1998 (136)	VLBWd	Preconceptional health	Black women and white women with an IPI of <6 months had a higher risk of VLBWthan those with an IPI of ≥12 months; black women had a higher prevalence of an IPI of <6 months than white women did.
Berg, 2001 (163)	VLBWd	Preconceptional health; substance abuse; SES; acute, chronic, or early- life stress	A significant racial difference in the risk profile for VLBW was found. SES markers were associated with white, but not black, VLBW. Only unmarried status, smoking, and no vitamin use during pregnancy were associated with VLBW for black women.
Andrews, 2006 (117)	VPT birthc	Preconceptional health, inflammation	Interconceptional antibiotic treatment in high-risk black women and white women did not change the risk of VPT birth.
Catov, 2007 (164)	VPT birthe	Preconceptional health, inflammation	Early-pregnancy elevated C-reactive protein and dyslipidemia levels double the risk of VPT birth for black women and white women (adjusted for but not stratified on race).
Jeffcoat, 2001 (53)	VPT birthc	Preconceptional health, inflammation	Periodontitis at 24 weeks increases the risk of VPT birth 7-fold and is more prevalent in black women than white women.
Offenbacher, 2006 (114)	VPT birthc	Preconceptional health, inflammation	Progression of periodontal disease during pregnancy doubles the risk of VPT birth for black women and white women (adjusted for but not stratified on race).
Dunlop, 2008 (120)	VLBWd	Preconceptional health, social support	A pilot trial of interconceptional primary medical and dental care with social support for black women with a prior VLBW birth reduced the risk of subsequent VLBW birth.
Ickovics, 2003 (144)	VPT birthc VLBWd	Preconceptional health, social support	Group-centered prenatal care for high-risk women resulted in a nonsignificant reduction in VLBW/VPT birth risk compared with standard prenatal care in a largely black study population.
Andrews, 2006 (112)	VPT birthc	Inflammation	Histologic evidence of inflammation in the placenta was more common in black women than white women with VPT birth.
Goldenberg, 1998 (46)	VPT birthc	Inflammation	Bacterial vaginosis and fetal fibronectin were more prevalent and were stronger predictors of VPT birth for black women compared with white women.
Adams, 2000 (89)	VPT birthc	Life course (SES? acute, chronic, or early-life stress? genotype/ epigenetics?)	Recurrent VPT birth is more common in black women than in white women.
Kistka, 2007 (88)	VPT birthb	Life course (SES, acute, chronic, or early-life stress? genotype/ epigenetics?)	VPT birth recurrence is greater for black women than for white women.
David, 1997 (165)	VLBWd	Life course (acute, chronic, or early-life stress?)	Among high-SES mothers, African-born blacks had a VLBW risk equivalent to that for whites, but US-born blacks had 3.3 times the risk compared with whites.
Shen, 2008 (166, 167)	VPT birthc	Life course (vascular dysfunction? genotype/ epigenetics?)	Black women were 2–3 times as likely as white women to have a VPT birth and PPROM or placental abruption; also found was a higher PPROM recurrence risk for black women compared with white women.
Collins, 2000 (77)	VLBWd	Interpersonal racism	Threefold elevated odds of VLBW were found for low-income black women reporting an experience of perceived racism during pregnancy.
Collins and Lespinasse, 2004 (76 and 78)	e, VLBWd	Interpersonal racism	Among black mothers, lifetime exposure to interpersonal racism was associated with VLBW.
Aveyard, 2002 (168)	VPT birthf	SES	SES accounts for a large portion of the Afro-Caribbean:white, but not African:white, disparity in the United Kingdom.
Kleinman, 1987 (169)	VLBWd	SES	The protective effect of a higher level of maternal education was greater for white women compared with black women.
Reagan, 2005 (170)	VPT birthe	SES; acute, chronic, or early-life stress; substance abuse; preconceptional health	Neighborhood poverty was associated with VPT birth in black women but not white or Hispanic women; tobacco, alcohol, and cocaine use was associated with VPT birth in white women but not black women.
Geronimus, 1996 (84)	VLBWd	SES; acute, chronic, or early-life stress–age	For black women but not white women, increasing maternal age was associated with VLBW risk, which was stronger for low-SES than high-SES black mothers.
Rauh, 2001 (86)	VLBWd	SES; acute, chronic, or early-life stress–age	Increasing maternal age increases VLBW risk for black women but not white women, a pattern exaggerated among Medicaid-eligible compared with -noneligible black women.
Schempf, 2007 (85)	VPT birthc	SES; acute, chronic, or early-life stress—age	Older, multiparous, black women have a higher risk of VPT birth than similar white women do, and this risk is not modified by SES.
Kramer, 2008 (171)	VPT birthc	Social environment	Black:white disparities vary significantly across US cities independent of individual SES, explained in part by degree of residential segregation and proportion of black women living in poverty.
Khashan, 2009 (71)	VPT birthe	Acute, chronic, or early-life stress	Risk of VPT birth for white Danish women in the index pregnancy increased if the mother experienced death or major illness of an older child in the 6 months prior to conception of the index pregnancy. This association persisted when analyses were restricted to mothers with a prior preterm birth.
Neggers, 2006 (61)	VPT birthc	Acute, chronic, or early-life stress	In a predominantly black population, women below the median on a psychosocial stress scale had a nonsignificant increased risk of VPT birth compared with those above the median on the stress scale.
Sable, 2000 (62)	VLBWd	Acute, chronic, or early-life stress	Perceived stress and major life events were associated with increased risk of VLBW for black women and white women (not stratified on race).
Nabukera, 2009 (172)	VPT birthc VLBWd	Acute, chronic, or early-life stress–age; preconceptional health	The black:white racial disparity in VLBW/VPT birth persists among women postponing their first pregnancy until after age 30 years. An IPI of <6 months is associated with VLBW/VPT birth in the second pregnancy.
Goldenberg, 2007 (173)	VPT birthc	Vascular dysfunction	Black women and white women with VPT birth had a similar prevalence of placental lesion, suggesting vasculopathy.
Yang, 2001 (174)	VPT birthc	Vascular dysfunction	Vaginal bleeding was associated with increased risk of VPT birth; a greater magnitude of effect was found in white women compared with black women.

Abbreviations: IPI, interpregnancy interval; PPROM, preterm premature rupture of membranes; SES, socioeconomic status; VLBW, very low birth weight; VPT, very preterm.

^aEntries in this column refer to nodes in Figure 2 that were evaluated in each study.

^bVPT birth was defined as <34 weeks’ gestation.

^cVPT birth was defined as <32 weeks’ gestation.

^dVLBW was defined as weight <1,500 g.

^eVPT birth was defined as <33 weeks’ gestation.

^fVPT birth was defined as <28 weeks’ gestation.